Abrading – Abrading process – Ring – tube – bushing – sleeve – or cylinder abrading
Reexamination Certificate
2000-06-23
2001-06-12
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Ring, tube, bushing, sleeve, or cylinder abrading
C451S041000, C451S049000, C451S164000
Reexamination Certificate
active
06244937
ABSTRACT:
The present invention relates to grinding wheels. More specifically, the invention relates to grinding wheels for grinding long slender shafts and a process therefore.
Cross reference is made to the following application filed concurrently herewith: U.S. patent application Ser. No. 09/146,207, entitled “Non-Contact Support for Cylindrical Machining”, by Grethel K. Mulroy et al.
To obtain precision parts for machines and other equipment, machining of the work surfaces of the components of parts of a machine are often required. To obtain high precision surfaces of parts and, in particular, to obtain precision surfaces for hard parts, for example ceramic or heat-treated steel parts, the work surfaces are machined by a hard, abrasive surface. For cylindrical workpieces the cylindrical outer periphery is often machined by simultaneously rotating the cylindrical part while rotating a cylindrical abrasive wheel. The part or workpiece is thus ground on a grinding machine.
The grinding of cylindrical parts is typically accomplished in one of two methods. In the first method, the workpiece is rotated about centers formed on the ends of the workpiece. Pressure on the workpiece centers or a drive dog attached to the workpiece is used to rotate the workpiece utilizing a motor in the head stock of the grinder. A grinding wheel having a generally cylindrical form is rotated by a grinding wheel spindle and driven by typically an electric motor. The periphery of the grinding wheel contacts the periphery of the rotating workpiece thereby performing the precision grinding of the periphery of the workpiece. This process is typically called cylindrical grinding.
Such grinding occurs by typically one of two processes, namely plunge grinding and traverse grinding. When utilizing plunge grinding, the grinding wheel is advanced toward the workpiece until the finished precision surface is obtained. In traverse grinding, the grinding wheel is brought into contact with the workpiece and caused to traverse in a direction parallel to the center line of the workpiece in a series of reciprocating motion until the final workpiece configuration is obtained.
One other type of cylindrical grinding is centerless grinding in which the workpiece is supported on the periphery of the workpiece in at least two places. For example, the workpiece is supported by a rest blade and a regulating wheel. The workpiece is contained within three different elements, the rest blade, the regulating wheel, and the grinding wheel.
As with cylindrical grinding, in centerless grinding, the grinding wheel may plunge into the workpiece until the final workpiece configuration is obtained or the grinding wheel may traverse along the axis of the workpiece until the final configuration of the workpiece is obtained.
The force of the grinding wheel against the workpiece during the grinding process creates a force upon the workpiece a portion of which is perpendicular to the workpiece contact surface causing the workpiece to deflect during the grinding process.
The deflection of the workpiece during grinding is a particular problem for precision, long or slender shafts. The deflection of the workpiece during the grinding may cause difficulty in obtaining precision size as the deflection during grinding changes with feed rates and grinding wheel configurations, as well as, with variations from workpiece to workpiece. Furthermore, surface conditions such as roundness, waviness, runout, cylindricity, as well as chatter, may become problems and are aggravated by the vibration from the grinder that may be transferred to the workpiece due to the deflection of the long, slender workpiece during the grinding process.
Long slender shafts are used extensively in machines that pass a substrate through the machine. For example, copy and printing machines pass either a series of cut sheets or a roll of substrate through the machine. The sheets or rolls are guided by long slender shafts and the work performed on the sheets and rolls are performed on long slender shafts. It should be appreciated that other types of machinery also use long slender rotating shafts to perform work.
In the well-known process of electrophotographic printing, a charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as “toner.” Toner is held on the image areas by the electrostatic charge on the photoreceptor surface.
Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate or support member (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
While shafts in electrophotographic printing for guiding substrates require accurate tolerances and may be long and slender, exasperating the accurate tolerance problems, the difficulties encountered in providing accurate donor rolls for scavengeless development systems is particularly acute.
In a scavengeless development system, toner is detached from the donor roll by applying AC electric field to self-spaced electrode structures, commonly in the form of wires positioned in the nip between a donor roll and photoreceptor in the case of hybrid scavengeless development or by applying the AC electrical field directly to the donor roll in the case of hybrid jumping development. This forms a toner powder cloud in the nip and the latent image attracts toner from the powder cloud thereto. Because there is no physical contact between the development apparatus and the photoreceptor, scavengeless development is useful for devices in which different types of toner are supplied onto the same photoreceptor such as in “tri-level”; “recharge, expose and develop”; “highlight”; or “image on image” color xerography.
Since hybrid scavengeless development relies on a continuous, steady toner powder cloud at the nip between the latent image and the donor roller and since the speeds at which the rollers operate in these complex machines may be very fast and the accuracy requirements of these rollers are quite precise.
The purpose and function of scavengeless development are described more fully in, for example, U.S. Pat. No. 4,868,600 to Hays et al., U.S. Pat. No. U.S. Pat. No. 4,984,019 to Folkins, U.S. Pat. No. 5,010,367 to Hays, or 5,063,875 to Folkins et al. U.S. Pat. No. 4,868,600 is incorporated herein by reference.
Developer or donor rolls utilized in the hybrid scavengeless development process typically have long slender diameters. For example, donor rolls may have lengths of approximately 19 inches and diameters of say, for example, 1.25 inches. The donor rolls may be made of anodized aluminum or ceramics. When manufactured from ceramics, the donor rolls are quite hard and very difficult to machine.
The donor rolls in hybrid scavengeless development require exacting tolerances to provide for accurate development of the latent image on the photoconductor and to avoid arcing or related problems. Donor rolls for hybrid scavengeless development may require exacting tolerances. For example, the donor rolls may require a runout having a total indicator runout (TIR) of say, for example, 20 microns, diameter of tolerances of, for example, in the order of several microns and surface finish in the single micron range.
In addition, due to vibrations in
DiGravio Thomas L.
Jaskowiak Timothy R.
Mulroy Grethel K.
Hail III Joseph J.
Ojini Anthony
Ryan Andrew D.
Xerox Corporation
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